Supporting Information. In summary, we predict that decorating the surface of MnO2 with Ti or Ge
could stabilize these oxides against anodic dissolution.
The scarcity of Ge makes it less attractive for large scale energy applications.16 On the other hand, Ti
is abundant and, in the form of TiO2, stable against dissolution up until 2.1 V at pH 0.28 On this
account, Ti is often used to stabilize materials against anodic dissolution. The most well-known
example of this, is the dimensionally stabilized anodes used for chlorine evolution, where Ti reduces
the corrosion of RuO2 electrodes.65,66 Moreover, several laboratories, including our own, have
recently demonstrated that layers of TiO2 can stabilize photoelectrodes against corrosion67–72.
Figure 3. Termination energies for a rutile (120) MnO2 surface where TiO2, GeO2, PtO2, RuO2,
SnO2 or IrO2 are covering the steps. The termination energy is plotted as function of the
surface formation energy of the guest dioxides, taken from ref.62 Both bridge and CUS steps
were modelled; however, there were only minor differences, up to 0.1 eV between the two
types of sites. Consequently, for clarity, we have only plotted the data for the bridge sites.
To summarize our theoretical findings: undercoordinated sites are the most prone to dissolution.
There is a thermodynamic driving force for TiO2 to selectively segregate to the undercoordinated
sites, due to its favorable surface formation energy. This should lead to an overall stabilization of the